Recently, a printed circuit board has required increased multilayer and density with the higher performance and smaller size of electronic equipment. By using an inner-through-hole connection for connecting ICs or parts at a minimum distance as a method for connecting layers of a board, the higher density can be obtained. According to the inner-through-hole connection, only the necessary layers can be connected, and the top layer of a board has no through hole and mounting properties are excellent. Japanese Laid-Open Patent No. 6-268345 (Japanese Patent Application. No. 5-77840) has proposed a printed circuit board (double-sided and multilayer printed circuit boards) having the inner-through-hole connecting structure in which an organic non-woven fabric is impregnated with a thermosetting resin to form a sheet board material (which is hereinafter referred to as a resin impregnated fabric sheet) a through hole is formed on the resin impregnated fabric sheet by laser beams, electrically conductive paste is filled in the through hole, and heat and pressure are applied to the resin impregnated fabric sheet.
The printed circuit board can be formed by the simple steps described above, in which the connecting resin impregnated fabric sheet is used to connect layers by the inner-through-hole connection. In addition, such a printed circuit board is inexpensive. In the case where the printed circuit board is used as a board for mounting a semiconductor of a chip size, the semiconductor can be mounted stably because the coefficient of thermal expansion of the board in the direction of a plane is almost equal to that of the semiconductor. However, the printed circuit board which is formed by the connecting resin impregnated fabric sheet has low thermal conductivity. Therefore, there are problems when the printed circuit board is used as a board for mounting a semiconductor chip. Moreover, an electrode land restricts an area on the top layer of the board in which wiring is formed (for example, the wiring for an electric connection with the semiconductor chip), so that high density wiring is not achieved.